imagetops: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/imagetops - from package: kdelibs3

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/imagetops - from package: netpbm

You may install the required package with command apt-get install {package}

Error in other languages:
imagetops: bevel nie gevind nie
imagetops: comandă negăsită
imagetops: comando não encontrado
imagetops: commande introuvable
imagetops: command not found
imagetops: käsku ei ole
imagetops: không tìm thấy lệnh
imagetops: komanda nerasta
imagetops: Kommando nicht gefunden.
imagetops: kommandot finns inte
imagetops: komut yok
imagetops: nie znaleziono polecenia
imagetops: níor aimsíodh an t-ordú
imagetops: no se encontró la orden
imagetops: no s'ha trobat l'ordre
imagetops: opdracht niet gevonden
imagetops: parancs nem található
imagetops: perintah tidak ditemukan
imagetops: príkaz nenájdený
imagetops: příkaz nenalezen
imagetops: команда не найдена
imagetops: командата не е открита
imagetops: 命令找不到
imagetops: コマンドが見つかりません